Application Guide for Cotton Fiber Whitening Agent 4BK
Time：2025-09-25Views：
I. Core Composition
Stilbene triazine and its derivatives, which ensure the whitening effect and stability of cotton fibers.
II. Basic Properties
- Appearance: Slightly reddish-purple to yellow powder (no caking indicates normal quality).
- Solubility: Relatively easy to dissolve in water (can be evenly dispersed with stirring at room temperature).
- Shade: Red light / Blue light; Ionicity: Anionic.
- Applicable pH Range: 7-10 (highest activity in neutral to weakly alkaline range; avoid exceeding this range to prevent reduced effectiveness).
III. Usage Method (Reference Formula for Exhaust Dyeing Process)
For cotton fiber whitening, prepare ingredients accurately in the following proportions (suitable for most conventional cotton and cotton-blended fabrics):
- Cotton Fiber Whitening Agent 4BK: Add 0.2-0.8% (o.w.f) (i.e., percentage relative to the weight of the fabric to be whitened). Adjust the dosage based on whitening requirements: use 0.2-0.4% for basic whitening (e.g., daily cotton fabrics) and 0.6-0.8% for high-whiteness requirements (e.g., white grey fabric, light-colored cotton fabrics). Avoid excessive dosage to prevent the fabric from turning greyish or bluish.
- 10% Sodium Sulfate Solution: Add 5-6% (relative to the total weight of the dye bath). First, pre-prepare solid sodium sulfate into a 10% aqueous solution (ensure complete dissolution without particles) before adding it to the dye bath. Its function is to promote the adsorption of the whitening agent on the cotton fiber surface and improve whitening uniformity.
- pH Adjustment: Use sodium carbonate (baking soda) to adjust the pH value of the dye bath to 7-9. Add sodium carbonate gradually while stirring gently, and confirm the value with pH test paper or a simple detector to ensure it stays stable within this range (pH fluctuations directly affect the activity of the whitening agent, leading to uneven local whiteness).
IV. Process Flow (Standard Operation Steps for Exhaust Dyeing)
1. Dye Bath Pre-treatment: First, add a sufficient amount of clean water to the dyeing vat (or container). Sequentially add the calculated amount of Cotton Fiber Whitening Agent 4BK and 10% sodium sulfate solution, then turn on low-speed stirring for 1-2 minutes to ensure the auxiliaries are evenly dispersed in the water. Next, add sodium carbonate to adjust the pH to 7-9, and stir again for 30 seconds to confirm no precipitation in the dye bath and stable pH.
2. Fabric Immersion & Temperature Rising: Put the cotton fabric to be whitened (pre-washed and drained of surface water to avoid oil stains or impurities) into the dye bath, ensuring the fabric is completely immersed without folding or piling. Start the heating device and slowly raise the temperature of the dye bath to 80°C (recommended heating rate: 5-8°C per minute). Prevent rapid temperature rise, which may cause local fabric contact with high-temperature auxiliaries and result in uneven whiteness.
3. Heat Preservation for Dyeing & Post-treatment: Once the temperature stabilizes at 80°C, maintain this temperature for 20-30 minutes of heat-preserved dyeing (gently turn the fabric 1-2 times during this period to ensure full contact between all parts of the fabric and the dye bath). After dyeing, first take out the fabric and rinse it with room-temperature clean water 1-2 times (to remove excess unadsorbed whitening agent on the surface and avoid whitish residue after subsequent drying). Then perform regular softening treatment (to improve fabric hand feel), and finally dry the fabric at 80°C to obtain the whitened finished product.
V. Packaging & Storage
- Packaging: 25kg kraft paper bags (moisture-proof and breathable, convenient for handling and batch management).
- Storage: Store in a room-temperature, dry, and well-ventilated place. The shelf life is 12 months in unopened condition. Once the package is opened, seal the bag tightly and use it as soon as possible (to avoid moisture absorption, caking, or volatilization of active ingredients, which may affect the usage effect).
